[compiler-rt] [test] env -u is not supported on AIX, use `unset` instead (PR #111736)

[Hubert Tong via llvm-commits]

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@@ -12,7 +12,8 @@
 // RUN: llvm-profdata show ./raw2.profraw | FileCheck %s -check-prefix TMPDIR
 //
 // Check that we fall back to the default path if TMPDIR is missing.
-// RUN: env -u TMPDIR LLVM_PROFILE_FILE="%%t/raw3.profraw" %run %t/binary 2>&1 | FileCheck %s -check-prefix MISSING
+// RUN: unset TMPDIR
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hubert-reinterpretcast wrote:

I see no sign that `unset` is implemented in the LIT built-in shell.

https://github.com/llvm/llvm-project/pull/111736